With rapid advance in technology and economy, almost every family is able to afford a motor vehicle, and thus there are more and more motor vehicles on the road. Consequently, with more and more cars being purchased each year and engines becoming even more efficient and technically specialized, driving safety is becoming an issue to be concerned.
Although the modern motor vehicles are more comfort, more technically advanced and more user friendly, there is still plenty to be improved regarding to the development in means for improving driving safety, especially for detecting and alerting vehicles approaching from the rear.
There are already many studies focused on the development in means for improving driving safety. One of which is a rear-view monitor disclosed in U.S. Pat. No. 6,218,960, which is designed for warning a driver of a host vehicle on which the rear-view monitor is mounted to respond to an vehicle approaching from the rear in the same lane or the adjacent lane according to an analysis based upon images of road in the rear of the host vehicle with regard to whether the rear-approaching vehicle is going to overtake the host vehicle, or the rear vehicle is approaching dangerously close to the rear of the host vehicle. Another such study is disclosed in JP Patent No. 2287799, which provides a method capable of detecting and determining whether there is any vehicle travelling in the adjacent lane that is approaching dangerously close to the host vehicle performing the method, and thus issuing an alert signal to a driver of the host vehicle as soon as the driver is changing lane into the path of the approaching vehicle so as to remind the driver that this lane-changing operation is dangerous for causing collision. Moreover, there is further another study disclosed in JP Pat. No. 7050769, which provides a method capable of using an optical flow analysis to determine whether the vehicle approaching from the rear or travelling in the adjacent lane is approaching dangerously close to the host vehicle performing the method while issuing a alert signal to the driver of the host vehicle when the host vehicle is in danger of colliding with the approaching vehicle.
Using the means provided in the aforesaid U.S. and Japanese patents, although any vehicle approaching or overtaking the host vehicle from the adjacent lane or an approaching vehicle in the adjacent lane that is travelling dangerously close to the host vehicle will be detected, and thereby triggers an alarm to be activated for warning the driver of the host vehicle, there are still plenty of other hazardous driving conditions that are remained unaccounted for. For instance, there can be a vehicle that is travelling on the same lane behind the host vehicle and abruptly performs a lane changing maneuver into one adjacent lane after it had approached dangerously close to the host vehicle, or there can be a vehicle that is approaching the host vehicle from the rear in one adjacent lane and abruptly performs a lane changing maneuver into the same lane of the host vehicle after it had approached dangerously close to the host vehicle; and nevertheless, in both case, the driver of the host vehicle should avoid performing any lane changing maneuver at the same time when the approaching vehicle is changing lane, and thus it is important for the driver of the host vehicle to aware at all time the relative distance between the host vehicle and the approaching vehicle. However, there is no study ever that is able to warn the driver for the aforesaid two hazardous driving conditions.
Therefore, it is in need of a warning method and system for detecting lane-changing condition of rear-approaching vehicles.